A variety of solar energy collectors have been proposed, particularly for use in areas in the middle latitudes which have a high percentage of sunlight. The energy produced may be used to desalinate water, produce thermal power for cooking or industrial operations, and a wide variety of similar uses. These devices all differ in their efficiency and in their cost and complexity. The present invention is accordingly directed toward a unit which is relatively simple in construction so as to be low in cost and reliable in operation and which converts a high percentage of the incident solar energy into useful thermal energy.